The secular Palestinian party Fatah, routed in the Gaza Strip by rival Hamas forces nearly three months ago, has begun to use political protest and reassemble its armed wing in order to resist the Islamic movement's tightening hold here.

Many Fatah officials fled Gaza during the decisive final days of fighting in June. Hamas has run a parallel administration in the strip since Palestinian Authority President Mahmoud Abbas, a Fatah leader, dissolved a power-sharing government led by Hamas.

The Fatah officials who remain keep a low profile, in part because Hamas's Executive Force, a 5,000-member paramilitary group, is deployed ostentatiously across the strip, seizing weapons and detaining Fatah followers. On Friday, amid scattered rallies across Gaza, Hamas forces arrested several senior Fatah officials, including Zakaria al-Agha, a member of the party's Central Committee. The officials were later released.

Fatah leaders here say the departure of its most divisive leaders has brought the opportunity for a fresh start in Gaza, where Hamas made inroads for years through its network of social service agencies, charities and sports clubs. They are also gambling that a U.S.-sponsored peace conference proposed for this fall will bring progress toward the creation of a Palestinian state, boosting the party's image as an effective alternative to Hamas's isolated administration. Hamas is classified as a terrorist organization by the United States and Israel.

"Over a few days this summer, Hamas showed that it cannot lead," said Ahmed Helles, 55, a member of the Fatah Higher Emergency Committee. "For us, having all of Fatah's 'gods' away from Gaza is going to help. And they weren't gods anyway, only statues."

As the party of the late Yasser Arafat, Fatah held a virtual monopoly on Palestinian political power until Hamas's victory in January 2006 parliamentary elections. Since then, Abbas, a member of the party's founding generation, and younger leaders clamoring for influence have been working with mixed results to change the party in anticipation of early elections.

Now the divide between Fatah in Gaza and in the West Bank, the seat of Abbas's U.S.-backed government, represents a new gulf within the party.

For more than a decade, Mohammed Dahlan, an Abbas protege and favorite of the United States, controlled the most powerful security services here. His authority over the cargo crossings into Israel also proved personally enriching.

Hamas never accepted the 1993 Oslo accords that created the semiautonomous Palestinian Authority. In the following years, Dahlan's Preventive Security Service detained, tortured and publicly humiliated many senior Hamas leaders.

At the time of the June fighting, Dahlan was involved in a U.S.-funded training program for Abbas's forces, as well as efforts to arm new Fatah recruits after suffering previous defeats this year by Hamas's military wing. He has since been fired as Abbas's national security adviser and remains in the West Bank. His home in the central Gaza city of Khan Younis has been looted.

"What is Fatah here?" Mahmoud al-Zahar, a Hamas leader, said in an interview. "I don't believe this is a real organization anymore. No one can even tell me now who the leader of Fatah is here."

Zahar, who advocates "military trial" for Fatah security officials, added caustically: "Maybe the big mistake we made was not giving Dahlan a chance to destroy Hamas? The American-Israeli collaborator failed."

Helles, long a Dahlan rival, exerts influence over Fatah's armed wing, the al-Aqsa Martyrs Brigades. His 17-year-old son, Mohammed, was killed in 2004 fighting against Israeli forces here, and the young man's face stares from a large framed picture in Helles's entry hall.

Like much else in the party, the al-Aqsa Martyrs Brigades has splintered in Gaza. Helles said he is working on drawing fighters back under one command, noting that "we're at the very beginning steps of this."

But Helles does not agree with some of Abbas's recent decisions. He criticized a decree Abbas issued this month that would effectively bar Hamas from future elections, and another to cut from the payroll about 30,000 government employees hired by the previous Hamas-led administration.

"In these ways, we look as bad as Hamas," said Helles, who talks regularly with Abbas by phone.

The most evident sign of Fatah's revival here are Friday demonstrations -- protests declared illegal by the Palestinian Scholars League, an Islamic council dominated by Hamas clerics. Thousands of people have turned out anyway. The Executive Force has responded with beatings and arrests.

"It is something we can no longer ignore," Helles said. "We know the campaign calling us traitors begins in the mosques. Demonizing us there as they do now is not their right."

The rising frustration within Fatah's rank and file has renewed the threat of factional violence. It is unclear whether the party's depleted and disorganized armed wing would stand a chance against the disciplined and numerous Hamas forces. "It is not Muslim what they are doing to us," said Nidal Darabaih, a 37-year-old taxi driver whose scalp bears a jagged white scar from a beating he suffered at a Friday rally. "But right now it seems we can't do anything about this."

Last week, the car of a well-known Hamas activist exploded outside his home. No one was injured in the blast, and a group calling itself the Security Members Martyrs Brigades asserted responsibility. The organization, probably very small, is believed to comprise former Fatah security officials who remain underground.

"We did not intend to have a coup in Gaza," said Ahmed Yousef, a political adviser to Ismail Haniyeh, the Hamas prime minister who was ousted by Abbas in June but continues to lead the administration in Gaza. "The situation for us was deteriorating, and we complained to President Abbas about it. But he did nothing to stop those causing the problems."

Yousef, who is involved in outside Arab efforts to reconcile Fatah and Hamas, said Abbas has frozen contact until after the peace conference this fall. No date or guest list has been set, although the target is November. Abbas has been meeting with Israeli Prime Minister Ehud Olmert on an agenda for the conference, and he has made clear that it must produce tangible progress toward the creation of a Palestinian state. Hamas leaders here say the conference will expose his political weakness, strengthening their own hand in eventual reconciliation talks.

"In a couple of months, Abu Mazen will figure out that counting on the Americans and the Israelis is a waste of time," Yousef said, using Abbas's nickname. "And he will see that Fatah has suffered from this delay."